This invention relates to a method for sweetening sour gas by delivering it to a semipermeable membrane which is highly permeable to particular sour gas components in the sour feed gas but is highly impermeable to methane and other fuel components in the feed gas.
It is a recognized goal to sweeten sour gas by removing the sour gas components, hydrogen sulfide and carbon dioxide. These acidic components are objectionable because they cause corrosion and their presence reduces the concentration of the desirable methane component so as to upset desired fuel levels. The hydrogen sulfide component is further objectionable because of its offensive smell and toxicity.
The prior art has been concerned with this problem and several methods for sweetening gas have been developed. Porter U.S. Pat. No. 3,534,528 discloses a bundle of semipermeable capillary filters to separate hydrogen sulfide from methane. Kimura U.S. Pat. No. 3,709,774 discloses methods of making asymmetric membranes composed of cellulose acetate, for use in gas separation. Merten et al. U.S. Pat. No. 3,415,038 discloses membranes for separating one gas from a mixture of gases wherein the pressure ratio of the gas across the membrane is 10,000:1.